Rear brakes locked up on my 931a2 while driving in traffic.

[Carlstealth]

I stopped for supper applied the parking brake came back after eating got in the truck and released the park brake drove about 3 miles with about 6 stops then the truck started to feel like the brake was on somewhat then after trying the brakes a couple times it locked up the rear wheels and wouldn't move. I tried everything like applying the hand brake and foot brakes and the dash push button in/out but now luck and there was a weird air sound like a vibration in the air stack that came and went. After about 20 min sitting with all brakes off it released and I could drive normal. I don't know if the foot break stuck on at the stop lights or the hand brake somehow came on. It did appear as though it was just the rear brakes that were applied when I tried rocking the truck.

Does anyone have any ideas what could have happened?

-So far I'm going to check the foot brake unit.
-Check the valve that the park break applies under the drivers doorstep.
-Looks like there is a relay valve on the drivers side air tank and take it apart and clean it.

 

[FASTNOVA]

It might be an issue with the parking brake, but it could be the the service brakes also. Were the brake lights on while this happened?

 

[quickfarms]

It could be sticking wedges, improperly adjusted brakes or leaking air chambers.

What was your air pressure when this happened?

 

[Carlstealth]

I'm not real sure about the break lights on I had the park lights on and they were lit for sure but i just glimpsed at them so not sure if break of park lights were what I looked at. If I had to guess one way I would say yes the break lights were on.

 

[Carlstealth]

Breaks are in new condition no air leaks at the pots its been fine before this happened and was normal when they released. I have a bad shutter stat because the engine and trans got up to 210.Also noticed the air intake trip sensor was half tripped so have to check the air filter as well.

It could be sticking wedges, improperly adjusted brakes or leaking air chambers.

What was your air pressure when this happened?

 

[Carlstealth]

Air pressure was 120 psi.

Breaks are in new condition no air leaks at the pots its been fine before this happened and was normal when they released. I have a bad shutter stat because the engine and trans got up to 210.Also noticed the air intake trip sensor was half tripped so have to check the air filter as well.

 

[MSenart]

Try checking your right front glad hand cover it should have a small hole in it or the type with a vent valve. If your cover has the vent valve ensure that it is clean and functioning as intended. Only the right front requires this vent function.

 

[Carlstealth]

Found out what happened to my brakes.Thanks to a question from FastNova. I vaguely recall that the break lights were on so I decided to check out the Treadle Valve. I took the 3 bolts out of the bottom and dropped the guts out and cleaned everything up nice. There was steel shot in it from a previous Truck Refit and lots of o-ring lube that had solidified. I would almost recommend taking this valve apart on all these and clean and service it before anything bad happens anyone else.It also had the lowest part of the valve rubber and washer in upside down and was wearing the body. I was glad I took it apart and hope there isn't more of this dirt anywhere else. I think I will look for a place to put a bit of air tool oil in the system.

 

[Carlstealth]

Vent valve was all good and in place where it should be. Thanks for the idea though.

Try checking your right front glad hand cover it should have a small hole in it or the type with a vent valve. If your cover has the vent valve ensure that it is clean and functioning as intended. Only the right front requires this vent function.

 

[Suprman]

The mil shutterstat is set for 205 I believe. The gage temp sender is at a different location from the shutterstat there can be a small temp difference and the gage is not always right anyways. I went with a 195 degree replacement my temp gage still says 205 when it comes on though. You can sometimes take the shutterstat apart and clean it up. You can test the fan clutch by blowing air into the line coming off the shutterstat going to the fan clutch it dosnt take much air to engage it.